Laserfiche WebLink
<br />, <br /> <br />information will define the flood magnitude on a <br />frequency basis for the 2, 5, 10, 25. SO, and 100 <br />year recurrence interval runoffs. These runoffs <br />shall be established for existing and projected land <br />uses. Flood plain maps shall he developed for each <br />flood interval and utilized to provide an estimate <br />of flood damage occurring from each flood. These <br />damages shall be related to the benefit derived by <br />reduction of area s~ject to flooding. <br />A3. The engineer shall consult with representatives of <br />local planning offices to obtain up-ta-date informa- <br />tion relative to development plans, right-oi-way, and <br />other items. <br /> <br />A4. Possible methods which might provide alleviation to <br />the existing flood hazard problems associated with the <br />subject basins shall be evaluated. The alternatives <br />shall include the following: <br /> <br />(a) Natural type water way <br />(b) Major underground conduit <br />(c) Relocating channel <br />(d) Use of lined flood channels <br />(e) Combination of any of the above <br /> <br />AS. The alternatives will be reviewed with an attorney who <br />is expert in Colorado drainage law. The attorney will <br />provide the engineer with a specific legal opinion on <br />each alternative. <br /> <br />A6. The engineer shall present a verbal report to the Dis- <br />trict, Lakewood, Jefferson, and Denver, outlining the <br />alternative plans, a review of the environmental impact <br />of the alternatives together with the advantages and <br />disadvantages of each, complete with estimated costs <br />for improvements and right-of-way. The engineer shall <br />also recommend one of the plans for adoption based on <br />all of the available inform<ltion and recommendation" <br />from the experts in the various disciplines involved. <br /> <br />B. Preliminary Design - Phase B <br />Once a decision is reached regarding the adoption of a <br />specific plan, the engineer shall undertake the necessary <br />work to prepare a preliminary design fo~ the subject drain- <br />age courses. <br /> <br />al. A final type hydrological study shall be prepared to <br />determine the magnitude and volume of flood runoff to <br />be used for design purposes. <br /> <br />-3- <br /> <br />oZ. D.,,,,i<,/n ..:riteri.. shall be developed specifically for the <br />subject project. <br />B3. Mapping shall be prepared at a scale of 1" equals 100' <br />with a contour interval of 2 feet through Oenver and 5 <br />feet through Lakewood. <br />B4. The approximate channel requirements will be outlined <br />upon the maps. Conferences will be held with local <br />officials in charge of planning, parks, greenbelts, and <br />engineering in order to best fit the channel character <br />and location with the requirements of these various <br />interests and disciplines. <br /> <br />as. Preliminary design shall be completed on the channel <br />showing flood plain, invert elevations, street crossings, <br />and approximate water elevations for the design flood. <br />86. Preliminary design drawings shall be prepared on 24~ x <br />36" sheets accompanied by a written report representing <br />the hydrological data, design criteria, and narrative <br />description of the preliminary design, together with <br />estimated costs of the work at present day prices. <br />Costs shall not include right-of-way. <br />It shOUld be noted that the scope of work deals with the <br />major gulches only and not with the numerous local drainage <br />problems in the vicinity of the gulches. To increase the benefit <br />of the study numerous references have been made in the text and <br />drawings to specific local drainage problems whiCh must be solved <br />by the individual entity. <br /> <br />METHOD OF ANALYSIS <br /> <br />A brief resume of the method of analysis utilized for this study <br />will be helpful to the reader to keep the following sections in <br />proper perspective. The following summary is divided into Phase <br />A and Phase B to coincide with the scope of work. <br /> <br />Phase A - The first step in Phase A was to become familiar with <br />the entire project using available mapping, aerial photographs, <br />field inspections, and studies of all available information. Once <br />a good grasp of the problem was obtained, development was initiated <br />on a hydrolo~ical computer prcgra~ tailo~-~~~~ fer tha needs vf <br />the Sanderson GulchjWeir GulCh project. It became evident that <br />this hydrological program must be capable of developing design <br />hydrographs for the six storm frequencies required, add and lag <br />individual hydrographs, route storm hydrographs through existing <br />and proposed reserviors, and develop runoffs from both exi~ting <br />and projected development. <br /> <br />+ <br />